where \(\Omega _H\)  is the angular velocity at the horizon and \(m_\phi \)  is the azimuthal number. Super-radiance amplifies the intensity of a wave and allows to extract energy and angular momentum from a rotating or charged BH [1]} very much as Penrose process [2]} uses particles to perform the same task, even in smooth horizonless geometries with an ergo-region [3]}, [4]}, [5]}, [6]}. The end-point of this ergo-region instability is expected to be a smooth horizonless BPS geometries [7]}.
